In semiconductor fabrication processes, effluent or exhaust gas from a process chamber must be treated chemically or physically before they can be released into a factory exhaust system and subsequently into the atmosphere. A large number of reactant gases utilized in the semiconductor fabrication processes and their reaction products are either highly flammable, toxic or foul-smelling. Some of the spent reactant gases exhausted out of a process chamber may contain gases that have not been reacted or have been partially reacted and therefore must be chemically treated before they can be released into the atmosphere. Gas treatment units such as gas reactor columns are frequently used for such purpose of converting toxic gases into non-toxic gases.
While a gas reactor column can be a hot bed reactor that treats a wide variety of gases in a single cartridge without creating additional effluent disposal problems, a simpler method of treating exhaust gases is the use of an absorption unit that functions on the principle of gas absorption into a porous substance without chemical reactions taken place. This type of physical absorption process can be carried out by using a bed of porous substance such as activated carbon for absorbing certain components in exhaust gases. Specifically, those of low boiling temperature and of foul-smelling.
For instance, in the exhaust gas exiting a photoresist stripper chamber, various toxic and foul-smelling gases are present. Typically, a photoresist solvent of ACT.RTM.-690 is used in a photoresist stripper chamber. Various high boiling temperature gases such as dimethyl sulfoxide (DMSO, C.sub.2 H.sub.6 SO), N-methyl pyrolidone (NMP, C.sub.2 H.sub.9 NO), methyl ethyl alcohol (MEA, C.sub.2 H.sub.7 NO) and various foul-smelling gases such as dimethyl sulfide (C.sub.2 H.sub.6 S), dimethyl disulfide (C.sub.2 H.sub.6 S.sub.2) and residual solvents such as isopropyl alcohol (IPA) and acetone are present in the exhaust gas. These major components are shown in FIG. 1. While the low boiling temperature gases, i.e., those having a boiling temperature of less than 100.degree. C. such as dimethyl sulfide, dimethyl disulfide, IPA and acetone can be successfully removed by an absorption apparatus filled with activated carbon as the absorption substance, the high boiling temperature gases such as DMSO, NMP and MEA carimot be effectively removed in the absorption apparatus. The total percentage of toxic, high boiling temperature gases removed from the exhaust gas therefore is poor and unacceptable when the exhaust gas is only treated by an absorption apparatus.
The following examples 1.about.3 illustrate results of the photoresist stripper chamber exhaust gas being treated by a conventional absorption method.